1. Field of the Invention
The invention relates to vehicle brakes and in particular to mechanically actuated parking brakes. More particularly, the invention relates to a parking brake construction having a pair of brake shoe operating levers which are actuated by a Y-shaped cable having a floating junction point which enables braking force to be applied to both brake shoes regardless of unequal brake shoe movement.
2. Description of the Prior Art
Numerous brake constructions for vehicles have incorporated therein both a hydraulic actuator for expanding the brake shoes outwardly into braking engagement with a drum upon applying the service brake, as well as a mechanical applying device for actuating the brake shoes upon applying a parking brake pedal or lever. Examples of such dual brake constructions are shown in U.S. Pat. Nos. 2,060,874, 2,127,739, 2,374,526, 3,023,853, 3,322,237, and 3,482,658.
Problems exist in many cable actuated parking brake constructions in that the brake shoes and actuating levers thereof have unequal movement due to the rotational force exerted on the shoes by the brake drum. One of the brake shoes becomes a leading shoe with the other brake shoe being a trailing shoe depending upon the rotational force exerted by the drum on the shoes. This force causes the shoes to move unequal distances with respect to the drum and backing plate creating unequal cable tensions for each shoe and in many instances preventing the parking brake force from being applied to one of the levers and associated shoe.
The brake constructions of U.S. Pat. Nos. 3,322,237 and 3,482,658 attempt to eliminate these problems by providing a sliding connection between a bellcrank actuating lever and a control cable which operatively connects the ends of brake shoe levers.
No parking brake construction of which I am aware eliminates the problems produced by unequal brake shoe movement by providing a Y-shaped actuating cable for operatively connecting the swinging ends of a pair of brake shoe levers to an operating handle, in which the Y-junction of the cable is freely moveable, the amount and direction of such movement being dependent upon the brake shoe movements.